
/**
 * @author  zhou-baicheng
 */
//下面是64个基本的编码

var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

var base64DecodeChars = new Array(

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,

52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,

-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,

15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,

-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,

41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);

// 编码的方法

function base64encode(str) {

	var out, i, len;

	var c1, c2, c3;

	len = str.length;

	i = 0;

	out = "";

	while (i < len) {

		c1 = str.charCodeAt(i++) & 0xff;

		if (i == len)

		{

			out += base64EncodeChars.charAt(c1 >> 2);

			out += base64EncodeChars.charAt((c1 & 0x3) << 4);

			out += "==";

			break;

		}

		c2 = str.charCodeAt(i++);

		if (i == len)

		{

			out += base64EncodeChars.charAt(c1 >> 2);

			out += base64EncodeChars.charAt(((c1 & 0x3) << 4)
					| ((c2 & 0xF0) >> 4));

			out += base64EncodeChars.charAt((c2 & 0xF) << 2);

			out += "=";

			break;

		}

		c3 = str.charCodeAt(i++);

		out += base64EncodeChars.charAt(c1 >> 2);

		out += base64EncodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));

		out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6));

		out += base64EncodeChars.charAt(c3 & 0x3F);

	}

	return out;

}

// 解码的方法

function base64decode(str) {

	var c1, c2, c3, c4;

	var i, len, out;

	len = str.length;

	i = 0;

	out = "";

	while (i < len) {

		do {

			c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];

		} while (i < len && c1 == -1);

		if (c1 == -1)

			break;

		do {

			c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];

		} while (i < len && c2 == -1);

		if (c2 == -1)

			break;

		out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));

		do {

			c3 = str.charCodeAt(i++) & 0xff;

			if (c3 == 61)

				return out;

			c3 = base64DecodeChars[c3];

		} while (i < len && c3 == -1);

		if (c3 == -1)

			break;

		out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));

		do {

			c4 = str.charCodeAt(i++) & 0xff;

			if (c4 == 61)

				return out;

			c4 = base64DecodeChars[c4];

		} while (i < len && c4 == -1);

		if (c4 == -1)

			break;

		out += String.fromCharCode(((c3 & 0x03) << 6) | c4);

	}

	return out;

}

function utf16to8(str) {

	var out, i, len, c;

	out = "";

	len = str.length;

	for (i = 0; i < len; i++) {

		c = str.charCodeAt(i);

		if ((c >= 0x0001) && (c <= 0x007F)) {

			out += str.charAt(i);

		} else if (c > 0x07FF) {

			out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));

			out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));

			out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));

		} else {

			out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));

			out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));

		}

	}

	return out;

}

function utf8to16(str) {

	var out, i, len, c;

	var char2, char3;

	out = "";

	len = str.length;

	i = 0;

	while (i < len) {

		c = str.charCodeAt(i++);

		switch (c >> 4)

		{

		case 0:
		case 1:
		case 2:
		case 3:
		case 4:
		case 5:
		case 6:
		case 7:

			// 0xxxxxxx

			out += str.charAt(i - 1);

			break;

		case 12:
		case 13:

			// 110x xxxx 10xx xxxx

			char2 = str.charCodeAt(i++);

			out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));

			break;

		case 14:

			// 1110 xxxx 10xx xxxx 10xx xxxx

			char2 = str.charCodeAt(i++);

			char3 = str.charCodeAt(i++);

			out += String.fromCharCode(((c & 0x0F) << 12) |

			((char2 & 0x3F) << 6) |

			((char3 & 0x3F) << 0));

			break;

		}

		return out;

	}

}

/*

// 编码

value = base64encode(utf16to8(src))



// 解码

value = utf8to16(base64decode(src))
 */